The website draws temperature data from thermometers located at meteorological stations around the world. For US stations, National Oceanic and Atmospheric Administration (NOAA)/National Climate Data Center (NCDC) bias-adjusted annual average values are used. They are taken from the file ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2.5/ushcn.v2.5.0.20130423. The Ocean heat content is for the top 2000 meters of the Ocean. Learn more about global ocean heat and salt content on the NOAA data center's website.